Safety device for pressing machines



Aug. 11, 1936. A. MATTHEWS 1 5 SAFETY DEVICE FOR PRESSING MACHINES Filed Sept. 11, 1933 INVENTOR ATTORNEYS.

Patented Aug. 11, 1936 UNITED STATES PATENT OFFICE SAFETY DEVICE FOR PRESSING MACHINES Application September 11, 1933, Serial No. 688,992

6 Claims.

This invention relates to a safety device for pressing machines, and more particularly to pressing machines of the scissors type having balance springs for normally retaining the pressing head in open position and the provision in such a machine of means for preventing the closing of the pressing members upon failure of the balance springs.

An object of the invention is to provide a safety latch arranged to automatically lock the pressing head to the frame of the pressing machine upon failure of the head balance springs.

Another object of the invention is to provide a safety means operable automatically to hold the pressing head of a power-operated press in open position upon failure of the head balance springs, said safety latch being arranged to prevent operation of the power means until the damaged springs are repaired.

A further objectof the invention is to provide a safety latch as above described, together with means for moving the latch to inoperative position automatically upon application of power to the power means.

Further objects and advantages of my improved safety device will be apparent from the accompanying description together with the drawing, and the essential features of which will be summarized in the claims.

In the drawing, Fig. 1 is a side elevation, partly in section, of a pressing machine embodying my invention; Fig. 2 is a partial side elevation showing the latching mechanism of Fig. 1 in latched position; Fig. 3 is a partial sectional view showing the latching mechanism in inoperative position; Fig. 4 is a section along the line 4-4 of Fig. 1; while Fig. 5 is a partial sectional view of valve mechanism for the power cylinder of Fig. 1.

I have illustrated my invention as applied to a press of the scissors type having the usual head lever provided with toggles, which in their straightened position move the head to closed position, and a balance or retriever spring for returning the head to open position. Upon failure of the balance spring in. such a press the head is likely to descend suddenly, which might cause injury to the operator. My safety device comprises in general a latch connected with the operating mechanism for the toggle, this latch normally lying in a position to intercept a coacting latch member on the press frame if the toggles should move toward straightened position due to failure of the balance spring. Means is provided, acting automatically upon application' of power to the power means for operating the press, which serves to move the latch to inoperative position, providing the balance spring and other Working parts of the press are in proper condition. However, if the balance spring has failed, the latching mechanism cannot be moved to inoperative position by this automatic means until the damage has been repaired.

I have chosen to illustrate my invention as applied to a press similar to that illustrated, described and claimed in the patent to Singiser, 2,006,751, granted July 2, 1935. Reference may be had to the said patent for a complete description thereof, and only sufficient description will be given here to permit an understanding of the operation of my improved safety device. The press illustrated in Fig. 1 comprises a frame l0 supporting a pressing bed H and a head lever l2 pivoted to the frame at I3. A pressing head It is mounted on the forward end of the head lever, and between the rear end of the head lever and the frame is arranged a balance or retriever spring l5 adapted to normally hold the head in open position. The usual toggles i6 and ill, pivoted together at their knuckle l8, are provided, straightening of which moves the pressing head to closed position. Power means is provided for closing the press, that illustrated comprising a cylinder is provided with a suitable piston 20 and a piston rod 2! which is operatively connected to the toggles so that movement of the piston rearwardly, or to the left in Fig. 1, straightens the toggles and closes the press. Control of fluid pressure to cylinder 59 is effected through a piston valve 22 in valve chamber 23, the piston being normally biased in the position of Fig. 5 when the press is open. In this position it will be noted that the passage 2d leading from cylinder l9 communicates through exhaust valve opening 25 with mufiler 26. The inlet of fluid pressure to valve chamber 23 is by means of inlet port 2? and conduit 2? under the control of operating handle 28 which may be a single member or preferably a two-hand control. Actuation of the operating handle opens a valve or valves 29 admitting fluid pressure through conduit 30 from a suitable source. Upon pressure entering valve chamber 23 through port 21' piston valve 22 is moved to the left in Fig. 5, thus closingexhaust port 25 and uncovering the passageway between the inlet end of valve chamber 23 and the passageway 24 leading to cylinder [9. Thereupon piston 20 is moved rearwardly and means is provided for setting up a maintaining circuit when the pressing members port in the passageway 24 leading to cyl'-- inder l9. This establishes maintaining pressure against piston 20 and the operator may then release the handle 23 or thetwo nand control,-

whichever is used.

To open the press the operator depresses foot treadle 4| which through .link. 42 moves bell crank 43 clockwise so that arm Moi the bell crank contacts stem 45 of piston valve 122 and moves the valve to the right (Fig. 5), thusopening exhaust port 25, permitting evacuation of cylinder IE to the atmosphere. with this action, a portion of arm 46 of bell crank 43 contacts a forwardly projecting cam surface 46 of bell crank 34 which serves to move that ,bell crank in a clockwise direction, thus removing the pressure from valve stem and permitting valve 37 to close, thus cutting off the supply of fluid pressure from source 38 to cylinder I9. The spring l5 then. returns the pressing head to open position.

My improved safety device comprises cooperating latch members, one of which is secured to the frame and the other connected withv the operating toggles and so arranged that the latch members coact to hold the pressing members in open position if the balance spring should fail. The embodiment disclosed comprises a latch member in the form of a bell crank 4! pivotallyv connected to downwardly extending lugs 48 on piston rod 2i. One arm of this bell crank is formed in the shape of a hook 49, and a pin 58 is supported from the frame or power cylinder in position to be engaged by the hook as the piston moves rearwardly to straighten the toggles. enters the hollow piston rod through a slot v53 Normally the parts he in the position shown in Fig. l where it will be observed that bell crank 41 is free to move in a counterclockwise direction to raise book 49 'to a position where it will fail to engage pin 50.- However, if'balance spring I5 should fail, the parts would move to the position shown in Fig. 2, where the toggles have straightened slightly, due to the failure of the balance spring, and hook 49 is firmly engaged with pin 50. This hook and 'pin connection is made sufliciently; strong that application of normal closing pressure to the parts in the posi tion of Fig. 2 will result in no action whatever, the parts 49 and 50 beingmade' sufficiently strong to withstand the action of the power means.

Means is provided for automatically moving the latch to inoperative position upon operation of the power means. The embodiment illustrated comprises a fluid actuated movable abut ment arranged to be supplied with fluid pressure simultaneously with the application of fluid pressure to the power cylinder. To this end I have illustrated piston rod 2| as being of hollow form and provided at one end with a movable abut ment orpiston 51 connected With a plungeror rod 52' which" is arranged for horizontarm'ove ment, in the courseof which it will normally contact the upwardly extending arm 53 'of bell Simultaneously The other arm 53 of the bell crank crank 41, thus moving the bell crank in a counterclockwise direction and moving the hook 49 to inoperative position as shown in Fig. 3. The plunger 52 may be provided with a bearing 5 to maintain its alinement, there being a collar 55 limiting the movement of piston 5| and its associated rod in one direction and there being a shoulder 56 adapted to contact piston 5! and limit its movement in the'other direction. A spring 57 normally biases piston 54 in its forward or right-hand position, as seen in the drawing. The forward end of the hollow piston rod 2i communicates with the passage 24 whereby fluid pressure being'supplied to power cylinder 19 will simultaneously enter the hollow piston rod and move the piston or abutment 5i rearwardly or to the left as seen in the drawing. Spring 51 is not a veryheavy spring, the result being that abutment 5! is moved to the limit of its movement almost instantaneously upon the application of pressure to cylinder l9; so that its action takes place before piston2il has made an appreciable movement. of abutment 5: causes plunger 52 to move the hook 49 to inoperative position as shown in Fig. 3, providing all the working parts of the press are in proper condition. It will be apparent, however, that withthe parts in the'position' of Fig. 2, consequent'upon failure of balance spring i5, application of pressure to the abutment 5i can cause no movement of the plunger 52 as the hook 49 is firmly engaged about the pin 55). Therefore the press cannot be" operated until the damaged parts havebeen repaired.

Means is provided for automatically returning -the parts of the safety mechanism to the posihorizontal and "cam surface 58 on "the backof the hook will cause the hook to be lifted" until it has passed pin' 50 on the return stroke:

It will thus be apparent that I have devised 'avery simple but'efiective safety mechanism for preventing accidental closing of the press head upon failure of the balance spring. The'mecha nism also prevents operation of the power means for operating the press during the continuance of such damaged condition. It will also be'noted that the safety'mechanism requires no-attention from theoperator'solong as theparts of the press are in proper" working condition and is released automatically each time that poweris applied to'thepress. It will furtherbenoted that the operating parts'requiredare few in" number and not likely to'get out of order.

What I claim is:'

1. In a press of the class described,the combination of coacting relatively movable pressing elements, powenmeansdo'r moving one of-said elements to close the press; means independent of the powermeansior normallfhbldiiigsaid element in open'position, safety means-auto matically operable to holdsaidelement inopen position upon failure of the second-named means, said safety means being arrangednor This preliminary movement- If, however, pressure is suddenly mally to prevent the operation of said power 76 means, and means for moving said safety means to inoperative position, said last-named means being operable by the flow of power to said power means.

2. In a press of the class described, the combination of coacting relatively movable pressing elements, power means for moving one of said elements, means independent of said power means for normally holding said element in open position, safety means automatically operable to hold said element in open position upon failure of the second-named means, said safety means being arranged normally to prevent efiective operation of said power means, means for moving said safety means to inoperative position, and means for actuating said last-named means automatically by application of power to said power means.

3. In a press of the class described, the combination of coacting relatively movable pressing elements, fluid pressure actuated power means for moving said elements, means for normally holding said elements in open position, safety means automatically operable to hold said elements in open position upon failure of the second-named means, said safety means being arranged normally to prevent the operation of said power means, and a fluid motor for moving said safety means to inoperative position, said motor being operable by application of fluid pressure to said power means.

4. In a press of the class described, the combination of coacting relatively movable pressing elements, means for closing said pressing elements including a cylinder, piston and hollow piston rod, a member arranged normally to prevent movement of said piston rod in press-closing direction, a movable abutment in said hollow piston rod, a connection between said abutment and said member for moving the member to an inoperative position upon movement of the abutment, and said abutment being operable by fluid pressure admitted to said cylinder.

5. In a press of the class described, the combination of a frame, coacting relatively movable pressing elements carried thereby, spring means for normally. holding one of said elements in open position, means for moving said element to closed position, and safety means for latching said last-named means to the frame when the press is open, said safety means comprising 00- operating latch parts normally in unlatched position and movable to latched position by slight movement of said element toward closed position upon failure of said spring means.

6. In a press of the class described, coacting relatively moving pressing members, a cylinder and piston motor for moving one of said members in press-closing direction, spring means for normally holding said one member in press-open position, latch means normally preventing pressclosing movement of said motor, said latch means comprising latch parts normally in unlatched position, and movable to latched position upon slight press-closing movement of said motor, a second fluid motor for moving said latch means to a position permitting pressclosing movement of said power means, and one fluid supply means for both motors.

ALBERT MATTHEWS. 

